Variable wave generator



July 29, 1941. M. WOLF 2,250,819

VARIABLE WAVE GENERATOR Filed May 26, 1939 SOURCE OF QC.

POTENTIAL\ OUTPUT INVENTOR MEN/v0 WOLF ATTO RNEY Patented July 29, 1941 VARIABLE WAVE GENERATOR Menno Wolf, Eindhoven, Netherlands, assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application May 26, 1939, Serial No. 275,800 In Germany June 1, 1938 4 Claims.

This invention relates to a device for the production of a periodical current or voltage Whose amplitude A increases with time.

According to the invention, the device comprises meansfor producing a saw-tooth current or voltage Whose frequency is equal to the number of leaps with which the amplitude of the current or voltage to be producedincreases and also means for producing a saw-tooth current or voltage whose frequency equals that of thecurrent or voltage to be produced, the saw-tooth currents or voltages produced being superimposed in opposite sense.

Such a device may be used, for example, in a multiple telephony system in which each of the conversation channels is periodically connected in succession to a common transmission line by means of a cathode ray tube that acts as a circuit element. As an alternative, the device is used for example in television arrangements comprising cathode ray tubes in which the image points are discontinuously scanned in succession.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully by Way of example with reference to the accompanying drawing, in which:

Figures 1 and 2 are explanatory curves.

Figure 3 is an embodiment of my invention.

Referring to Fig. 1, the amplitude A is illustrated as a function of the time t of a current or voltage which is to be produced by means of a device according to the invention. According to the invention such a current or voltage may be obtained by superimposure of two saw-tooth currents or voltages A1 and A2 illustrated in Fig. 2 as a function of the time t. A A represents the change in amplitude or, as has been expressed hereinbefore, the leap in amplitude which takes place in the sawtooth wave in a step by step manner, the entire sawtooth wave being built up in a fashion whereby the amplitude increases in incremental steps which continue at a constant amplitude for a predeterminable period of time.

A device for producing the current or voltage shown in Fig. l consequently comprises a device for producing the saw-tooth oscillation A1 shown in Fig. 2 whose oscillation time equals the oscillation time T( f=frequency of the current or voltage to be produced and in addition a device for producing the saw-tooth oscillation A2 shown in Fig. 2 whose oscillation time 1' is equal to the time T divided by the number of leaps occurring in the oscillation time T.

Devices for producing the saw-tooth oscillations A1 and A2 general comprise a condenser which is charged by a source of direct voltage across a resistance and discharges, for example, across a discharge tube. The production of the oscillation A2 in this manner presents no difficulty but in producing the oscillation A1, which has a substantially larger oscillation time, there is the disadvantage that the condenser voltage no longer increases linearly with time. In this case, the amplitude A of the oscillation obtained by superimposure of the oscillations A1 and A2 is not constant during each time 1- but decreases.

Referring to Fig. 3 there is shown one embodiment of my invention. In this figure there are provided two gas filled discharge tubes V1 and V2, the cathode of V2 being connected directly to the anode of V1. The control grid of V2 is biased negatively with respect to the oathode thereof by means of the source of constant bias potential B2 and a potentiometer shunted there across, the control grid being connected to the sliding arm of the potentiometer and the cathode being connected to one fixed terminal thereof. Similarly, the control grid of V1 is biased negatively with respect to the cathode thereof by means of the source of constant bias potential B1 with its appurtenant potentiometer. Condenser C1 is shunted directly across the anode and cathode of tube V1 and condenser C2 is shunted directly across the anode and cathode of tube V2. Condensers C1 and C2 therefore have a common terminal which is indicated as the point P. A source of fixed potential E is connected serially with respect to both condensers C1 and C2, the negative terminal of the source E being connected through a series connected resistor R1 to the uncommon terminal of condenser C1, and the positive side of source E being connected to the uncommon terminal of condenser C2 through serially connected resistor R2. negative terminal may be grounded if desired. Condensers C1 and C2 are in general equal in value, but not necessarily so. The output may be taken from the negative terminal of resistor R1 and the common terminal of condensers C1 and C2. This has been identified in the drawing as the output. The condensers C1 and C2 discharge respectively across a gasfilled discharge tube V1 and V2 Whose starting-upvoltage is so adjusted by means of a negative bias supplied from a source of voltage B1, B2 and transmitted to the grid that the condenser C1 discharges after a time T, the condenser. C2 after a time 1. As a result of the charging up of the condenser C1 the voltage of the point of connection P of the condensers C1 and C2 relatively to a point of constant potential, for example the negative terminal of the source of voltage E, increases linearly from an initial value /;;E during the time T and this increase corresponds to the curve A1 of Fig. 2. Owing to the charging up of the condenser C2 the voltage of the point P relatively to the negative terminal of the source of voltage E decreases from an initial value E during the time 1' and this decrease corresponds to the curve A: of Fig. 2. The voltage of the point P relatively to the negative terminal of the source of voltage E thus varies according to a curve given by the sum of A1 and A2 and shown in Fig. 1. In the circuit arrangement described the condensers C1 and C2 are connected in series so that they are charged up by the same current. This ensures that the increase of the voltage of the point P during each time 1- due to the charging up of the condenser C1 corresponds to the decrease in voltage of the point P consequent upon the charging up of the condenser C2 so that the amplitude A of the voltage produced in the point P is constant during each time 7' and the voltage produced thus passes abruptly from one exactly constant value to the next following value which is also exactly constant.

What I claim is:

1. Apparatus for producing a step by step serrated wave form comprising a plurality of electrical storage means, means for linearly storing energy in each of said storage means at a differing rate, means for discharging at least a portion of the stored energy in each of said storage means and means for combining said stored en ergy in all of said storage means in such phase as to substantially cancel out a portion of the stored energy.

2. The method of producing a step by step serrated Wave form which comprises the steps of developing a plurality of substantially linearly stored discrete electrical charges in differing time intervals, and combining said stored charges in such phase as to substantially cancel out a portion of the stored energy in at least one of the stored charges.

3. Apparatus for producing a step by step serrated wave form comprising a pair of condensers having one terminal thereof commonly connected, means for linearly storing energy in each of said condensers at a difiering rate, thermionic discharge means having said condensers connected in the anode-cathode path thereof, and an output circuit having one side thereof connected to the common terminal of the condensers and the other side thereof connected to one terminal of the means for storing energy in said condensers.

4. Apparatus in accordance with claim 3 wherein the thermionic discharge means comprise a pair of thermionic tubes, each having one of said. condensers shunted across the anode and cathode thereof.

MEN'NO WOLF. 

